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.Dd September 23, 2025
.Dt PSIGNAL 3
.Os
.Sh NAME
.Nm psignal ,
.Nm psiginfo ,
.Nm strsignal ,
.Nm sys_siglist ,
.Nm sys_signame ,
.Nm sig2str ,
.Nm str2sig
.Nd system signal messages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft void
.Fn psignal "int sig" "const char *s"
.Ft void
.Fn psiginfo "const siginfo_t *si" "const char *s"
.Vt extern const char * const sys_siglist[] ;
.Vt extern const char * const sys_signame[] ;
.In string.h
.Ft "char *"
.Fn strsignal "int sig"
.Ft int
.Fn sig2str "int signum" "char *str"
.Ft int
.Fn str2sig "char *str" "int *pnum"
.Sh DESCRIPTION
The
.Fn psignal
and
.Fn strsignal
functions locate the descriptive message
string for a signal number.
.Pp
The
.Fn strsignal
function accepts a signal number argument
.Fa sig
and returns a pointer to the corresponding message string.
.Pp
The
.Fn psignal
function accepts a signal number argument
.Fa sig
and writes it to the standard error.
If the argument
.Fa s
is
.Pf non- Dv NULL
and does not point to the null character,
.Fa s
is written to the standard error file descriptor
prior to the message string,
immediately followed by a colon and a space.
If the signal number is not recognized
.Pq Xr sigaction 2 ,
the string
.Dq "Unknown signal"
is produced.
.Pp
The
.Fn psiginfo
function is similar to
.Fn psignal ,
except that the signal number information is taken from the
.Fa si
argument which is a
.Vt siginfo_t
structure.
.Pp
The message strings can be accessed directly
through the external array
.Va sys_siglist ,
indexed by recognized signal numbers.
The external array
.Va sys_signame
is used similarly and
contains short, upper-case abbreviations for signals
which are useful for recognizing signal names
in user input.
The defined variable
.Dv NSIG
contains a count of the strings in
.Va sys_siglist
and
.Va sys_signame .
.Pp
The
.Fn sig2str
function translates the signal number
.Fa signum
to the signal name, without the
.Dq SIG
prefix, and stores it at the location specified by
.Fa str ,
which should be large enough to hold the name and the terminating
.Dv NUL
byte.
The symbol
.Dv SIG2STR_MAX
gives the maximum size in bytes required.
.Pp
The
.Fn str2sig
function translates the signal name
.Fa str
to a signal number and stores it in the location referenced by
.Fa pnum .
The name in
.Fa str
can be either the name of the signal, with or without the
.Dq SIG
prefix, or a decimal number.
.Sh RETURN VALUES
The
.Fn sig2str
and
.Fn str2sig
return 0 on success and -1 on translation failure.
In the latter case the memory to store the translation result is left intact.
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr perror 3 ,
.Xr strerror 3
.Sh STANDARDS
The
.Fn psignal
and
.Fn psiginfo
functions are defined by
.St -p1003.1-2008
, while the
.Fn sig2str
and
.Fn str2sig
functions are defined by
.St -p1003.1-2024 .
.Sh HISTORY
The
.Fn psignal
function appeared in
.Bx 4.2 .
The
.Fn psiginfo
function appeared in
.Fx 14.3 ,
.Nx 6.0 ,
and
.Dx 4.1 .
The
.Fn sig2str
and
.Fn str2sig
functions appeared in
.Fx 15.0 .
